Description
VpCI®-371 is a fast-drying solvent-based silicone coating applied direct to metal and rated for service to 1,200°F. This is the one for stacks, exhaust, ovens and anything else that gets genuinely hot. Cortec lists it as VpCI-371 Aluminum; the 5-gallon pail covers roughly 300 to 590 sq ft at the recommended film.
Conventional corrosion coatings burn off above a few hundred degrees, which is why oil-cooler headers, exhaust manifolds, heat exchanger shells and stack sections so often end up in stainless. VpCI-371 is an aluminum-pigmented silicone that keeps its film and its corrosion inhibitors at 400 to 1,200 °F, and in Cortec field work it has let an OEM go back to carbon steel with a coating instead of paying for stainless. It also handles harsh, unsheltered outdoor exposure and high UV. Cortec lists VpCI-371 among its permanent high-performance coatings for carbon steel, stainless steel, cast iron, aluminum and galvanized steel; its application guide calls for VpCI-373 wash primer first on aluminum, galvanized or plated substrates. It is solvent-borne at 3.3 lb/gal VOC with a 77 °F flash point, so it ships as a flammable liquid and needs a permitted booth or open-air application.
Typical applications
- High-temperature equipment (400–1,200°F)
- Harsh outdoor unsheltered environments
- High-UV exposure areas
- Multi-metal direct-to-metal protection
- Oil-cooler headers and heat exchanger shells on heavy equipment
- Exhaust manifolds, mufflers and stacks
- Ovens, furnaces, boilers and dryer housings
- Carbon steel components that would otherwise be specified in stainless
How to apply VpCI-371
- Surface preparation. The substrate must be free of grease, oil, dirt, fingerprints, drawing compounds, rust inhibitors and anything else that would affect adhesion. Cortec recommends VpCI-440 or a similar phosphatizing pretreatment on production lines and a minimum of NACE No. 3 / SSPC-SP6 commercial blast on structural steel. On aluminum, galvanized or plated substrates apply VpCI-373 wash primer at 0.5 to 1.0 mil first and test adhesion before full-scale work.
- Mixing and dilution. Power-agitate to a uniform consistency with a squirrel-cage or drill mixer so the aluminum pigment is fully suspended. VpCI-371 may be thinned with xylol or t-butyl acetate up to 10 % by volume; ask Cortec or us before going further.
- Conditions. Apply between 45 and 90 °F (7 to 32 °C) with the surface at least 5 °F (2 °C) above the dew point. Ground the equipment and keep ignition sources clear; the flash point is 77 °F (25 °C).
- Equipment. Spray, roll, brush or dip. HVLP or conventional spray: 0.009 to 0.021 in tip, 45 to 55 psi air and 10 psi fluid, 3/8 in ID fluid hose no longer than 50 ft, dual-regulated pot kept at gun height. Airless or air-assisted airless: 0.015 to 0.035 in tip, 1,800 to 2,500 psi, 3/8 in ID hose (a 1/4 in whip end is fine) no longer than 100 ft. Tip size depends on pressure and viscosity.
- Film build. Apply 1.0 to 2.0 mils (25 to 50 µm) dry, 3.0 to 5.4 mils wet. Theoretical coverage is 593 sq ft per gallon at 1.0 mil DFT. Do not overbuild; thin films perform best at temperature.
- Drying and heat cure. Dry to touch in about 20 minutes and dry to handle in about 40 minutes; recoat between 40 minutes and 72 hours, sanding after that. Force-dry 15 to 20 minutes at 150 °F (65 °C) if needed. Full ambient cure takes 3 to 7 days; for full hardness heat-cure 30 minutes at 500 °F (260 °C), or let the first service heat-up do it.
- Cleanup. Clean tools with butyl acetate while wet; once dry use butyl cellosolve or MEK, following the solvent manufacturer’s safety directions.
- Storage. Keep the container sealed, protect from freezing and do not store above 100 °F (38 °C). Shelf life is 1 year.
- See the Cortec coatings application guides and comparison table for the shared spray, prep and storage instructions across the Cortec coating range.
Where it fits in the Cortec line
VpCI-371 is the only Cortec coating for hot service. For ambient structural steel the water-based direct-to-metal topcoat is VpCI-386, the one-coat acrylic VpCI-375 gives the highest published salt spray in the line, VpCI-396 moisture-cure urethane handles marginally prepared steel and immersion, and VpCI-395 is the two-component epoxy primer. On aluminum or galvanized parts start with VpCI-373. For rusted steel that cannot be blasted, derust with VpCI-422 or convert the rust with CorrVerter before coating; where blasting is possible, an abrasive blast room gets you to SSPC-SP6 fastest. Browse the full Cortec VpCI line.
Field notes
A heavy-equipment OEM found carbon-steel oil-cooler headers severely corroded at preventive-maintenance intervals and had switched to stainless steel. Cortec proposed carbon steel with VpCI-371 at 1.0 to 2.0 mils DFT. The coated steel passed ASTM B117 600-hour salt spray, ASTM D714 blistering, ASTM D1654 scribe corrosion and ASTM D3363 hardness (reported as 5B ambient-cured and 9H after full cure), and the OEM specified VpCI-371 in place of stainless with large material savings (Cortec field data). Cortec cites ASTM D2485 for the high-temperature service rating.
Specifications
| Service temperature | 400–1,200°F |
|---|---|
| Salt spray (ASTM B117) | 600 hours |
| VOC (ASTM D3960) | 3.3 lbs/gal (395 g/L) |
| Volume solids | 37.1% |
| Recommended DFT | 1.0–2.0 mils (25–50 µm) |
| Coverage | 593 ft²/gal @ 1.0 mil DFT |
| Gloss | 80+ |
| Flash point | 77°F (25°C) — flammable liquid, hazmat shipping applies |
| Shelf life | 1 year |
| Type | Solvent-based aluminum-pigmented silicone, direct to metal; permanent coating |
| Color | Aluminum |
| Recommended WFT | 3.0–5.4 mils (75–135 µm) |
| Viscosity | 30 s+ Zahn #3 |
| Weight per gallon | 8.84 lb (1.06 kg/L) |
| Dilution | Xylol or t-butyl acetate, up to 10% by volume |
| Dry to touch / dry to handle | 20 min / 40 min |
| Recoat | 40 min – 72 hr; sand thereafter |
| Force dry | 15–20 min at 150 °F (65 °C) |
| Full cure | 3–7 days ambient; heat cure 30 min at 500 °F (260 °C) |
| Hardness (ASTM D3363) | 5B at dry-to-touch; 9H after the full 500 °F heat cure |
| Adhesion (ASTM D3359) | 5B; flexibility ½″ mandrel (ASTM D522) |
| Standards cited | ASTM D2485 high-temperature service; ASTM B117, D714, D1654, D3363 |
| Surface preparation | Clean and contaminant-free; NACE No. 3 / SSPC-SP6 on structural steel; VpCI-373 wash primer on aluminum, galvanized or plated |
| Application temperature | 45–90 °F (7–32 °C), surface 5 °F above dew point |
| Metals | Carbon steel, stainless steel, cast iron, aluminum, galvanized steel |
| Storage | Original packaging, indoors, out of direct sunlight, 40–100 °F (4–38 °C); keep from freezing |
| Size | 5 Gallon Pail |
| Shipping weight | 46.2 lb (21.0 kg) |
| Availability | In stock |
| Cortec product number | 12400321 |
Solvent Recycling Systems is an authorized Cortec® distributor. See the full Cortec VpCI line, browse the VpCI product selection guide, or contact us for volume pricing and lead times.
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